"I feel proudest", he said, addressing the conference. He said twin girls with the altered genes were born earlier this month.
In light of the global outcry against disgraced researcher He Jiankui, China's Vice-Minister of Science and Technology has confirmed his ministry has ordered a halt to the condemned human gene-editing work.
But details of the experiment, which has not been independently verified, triggered an immediate backlash and He said the trial had been "paused". "For this specific case, I feel proud, actually, I feel proudest". "[An] HIV vaccine is not available", he said.
The National Health Commission has already said Prof He's work "seriously violates China's laws, regulations and ethical standards" and would investigate the claims. He also emphasised that he informed the couples involved in the study of the risks of the removal of the CCR5-related gene, which he deleted in the twins using gene-editing tool Crispr.
Dr He, responding to questions from the audience, said: "The volunteers were informed of the risks posed by the existence of one potential off-target, and they made a decision to implant".
There has been wide condemnation of the unproven claim by He, who appeared this week at an worldwide conference on gene editing in Hong Kong.
Upon questioning, He even dropped this bombshell: "There is another one, another potential pregnancy", suggesting that there could be a second pregnancy with gene-edited babies. His appearance at the summit left participants, which included prominent gene-editing researchers, with more questions than answers.
A group of leading scientists has declared it is too soon to try making permanent changes to DNA that can be inherited by future generations, as a Chinese researcher claims to have done.
He, who said he was against gene enhancement, said eight couples were initially enrolled for his study while one dropped out. This indicates that the research of gene editing in China not only has a promising potential, but is also responding to the public's needs, stated Liang Chen, a professor at Sun Yat-Sen University.
On Tuesday, China ordered a "thorough investigation" into the project, but as the Associated Press is reporting today, the government has now taken the added step of shutting down the work until further notice.
After He spoke, David Baltimore, a Nobel laureate from the California Institute of Technology and a leader of the conference, said He's work "would still be considered irresponsible" because it did not meet criteria many scientists agreed on several years ago before gene editing could be considered. "Had he been more open with what he was doing, it could have been part of a national or worldwide discussion", he said.
Conference moderator Robin Lovell-Badge said the summit organisers were unaware of the story until it broke this week.
Dr He, who was educated at Stanford University, said the twins' DNA was modified using CRISPR, a technique that allows scientists to remove and replace a DNA strand with pinpoint precision. "We only found out about it after it happened, and after the children were born", Baltimore said on stage.